[TG3]: WoL fixes.

Change TG3_FLAG_SERDES_WOL_CAP to TG3_FLAG_WOL_CAP to make it easier
to manage WoL.  This flag is now used consistently during ethtool WoL
setup and power setting changes.

Signed-off-by: Gary Zambrano <zambrano@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>